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  2. Lanthanide - Wikipedia

    en.wikipedia.org/wiki/Lanthanide

    The lanthanide (/ ˈlænθənaɪd /) or lanthanoid (/ ˈlænθənɔɪd /) series of chemical elements [a] comprises at least the 14 metallic chemical elements with atomic numbers 57–70, from lanthanum through ytterbium. In the periodic table, they fill the 4f orbitals. [2][3][4] Lutetium (element 71) is also sometimes considered a lanthanide ...

  3. Lanthanum - Wikipedia

    en.wikipedia.org/wiki/Lanthanum

    Lanthanum. Lanthanum is a chemical element; it has symbol La and atomic number 57. It is a soft, ductile, silvery-white metal that tarnishes slowly when exposed to air. It is the eponym of the lanthanide series, a group of 15 similar elements between lanthanum and lutetium in the periodic table, of which lanthanum is the first and the prototype.

  4. Block (periodic table) - Wikipedia

    en.wikipedia.org/wiki/Block_(periodic_table)

    Blocks (s, p, d, f, ...) A block of the periodic table is a set of elements unified by the atomic orbitals their valence electrons or vacancies lie in. [1] The term seems to have been first used by Charles Janet. [2] Each block is named after its characteristic orbital: s-block, p-block, d-block, f-block and g-block.

  5. Lanthanide contraction - Wikipedia

    en.wikipedia.org/wiki/Lanthanide_contraction

    Lanthanide contraction. The lanthanide contraction is the greater-than-expected decrease in atomic radii and ionic radii of the elements in the lanthanide series, from left to right. It is caused by the poor shielding effect of nuclear charge by the 4f electrons along with the expected periodic trend of increasing electronegativity and nuclear ...

  6. Actinide - Wikipedia

    en.wikipedia.org/wiki/Actinide

    In presentations of the periodic table, the f-block elements are customarily shown as two additional rows below the main body of the table. [1] This convention is entirely a matter of aesthetics and formatting practicality; a rarely used wide-formatted periodic table inserts the 4f and 5f series in their proper places, as parts of the table's ...

  7. Actinoid contraction - Wikipedia

    en.wikipedia.org/wiki/Actinoid_contraction

    It is more pronounced than the lanthanoid contraction because the 5f electrons are less effective at shielding than 4f electrons. [1] It is caused by the poor shielding effect of nuclear charge by the 5f electrons along with the expected periodic trend of increasing electronegativity and nuclear charge on moving from left to right.

  8. Electron configurations of the elements (data page) - Wikipedia

    en.wikipedia.org/wiki/Electron_configurations_of...

    This page shows the electron configurations of the neutral gaseous atoms in their ground states. For each atom the subshells are given first in concise form, then with all subshells written out, followed by the number of electrons per shell. For phosphorus (element 15) as an example, the concise form is [Ne] 3s 2 3p 3.

  9. Periodic table - Wikipedia

    en.wikipedia.org/wiki/Periodic_table

    The periodic table, also known as the periodic table of the elements, is an ordered arrangement of the chemical elements into rows ("periods") and columns ("groups"). It is an icon of chemistry and is widely used in physics and other sciences. It is a depiction of the periodic law, which states that when the elements are arranged in order of ...